Have you ever thought about why you are required to perform certain maneuvers on a private pilot check ride? While some maneuvers like short field landings make total sense, others may not. Take slow flight for example. Why fly slow, when the point of flying (most of the time) is to go fast?
Low And Slow - The Reason Behind The Maneuver
Slow flight is evaluated on the private check ride because of its similarities to flying the traffic pattern, where you are low, slow, and operating on a different part of the power curve. Why is this important? Aircraft flying on the "back side" of the power curve behave much differently, but we'll get to that in a minute.
Another reason slow flight is evaluated is for stall/spin awareness. In the traffic pattern you fly closer to stall speed, and you're performing turns at up to 30 degrees of bank. If you don't maintain coordinated turns and sufficient airspeed, your chances of stall/spin increase.
How Slow Flight And Cruise Flight Differ
When you demonstrate slow flight on a check ride, you are required to fly at an airspeed "at which any further increase in angle of attack, increase in load factor, or reduction in power, would result in an immediate stall", according to the Private Pilot Practical Test Standards.
Flying at this speed means that you are on the back side of the power curve, also known as the "region of reversed command." In normal cruise flight, you pitch the aircraft to maintain altitude, and power the aircraft to maintain airspeed. However on the back side of the power curve the inputs are opposite. You pitch the aircraft to maintain airspeed and use power to maintain altitude. Why is this? The answer lies in induced drag, which dramatically increases as the aircraft's angle-of-attack (AOA) increases to maintain sufficient lift at low airspeeds.
By mastering (and demonstrating to your check pilot) that you can successfully fly an aircraft on the back side of the power curve, you're also demonstrating your ability to safely fly an aircraft on final approach to landing. On final, you use the same inputs as in slow flight: pitch for altitude and power for glide path. Once you've got the concept down for slow flight, maintaining a stabilized approach to landing becomes much easier.
Avoiding Stall/Spin Accidents - Maintaining Coordinated Flight
As I mentioned before, the second reason slow flight is demonstrated on a check ride is stall/spin awareness. Maintaining coordinated flight is always important, but it becomes crucial at slow airspeeds. Since a spin is caused by an aggravated and uncoordinated stall, maintaining coordination and sufficient airspeed in the traffic pattern is paramount.
According to AOPA, stall/spin accidents tend to be more deadly than other types of GA accidents, accounting for about 10 percent of all accidents, but 13.7 percent of fatal accidents. Overall, stall/spin accidents in the traffic pattern have a fatality rate of about 28 percent.
By managing your aircraft along the power curve and maintaining coordinated flight, you'll ensure that you ace slow flight on your check ride, and that you're always flying safely in the traffic pattern.
Do you have a story about performing slow flight on a checkride or during your flight training? Share it in the comments below!
